Party members voted to support the deal to enter government at Saturday morning's extraordinary general meeting (EGM) following a two-hour debate.
The Scottish Greens' Party Council will still have to approve the deal by a two-thirds majority.
With proxy votes still to be counted, 715 members (88.5%) had backed the deal, 84 (10.4%) voted against and nine (1.1%) abstained.
The outcome of that final decision is expected to be announced by co-leaders Patrick Harvie and Lorna Slater at a press conference scheduled to begin at 3pm.
The pair would become government ministers under the powersharing deal, with the Greens required to back the Scottish Government in confidence votes and annual budgets as they work on a raft of agreed policy areas, including tackling the climate emergency, Scottish independence and rent controls.
Public disagreement between the parties would only be allowed on a set of agreed topics, such as aviation policy, green ports, direct financial support to businesses involved in the aerospace, defence and security sectors, field sports and the economic principles related to concepts of sustainable growth and inclusive growth.
However, speaking during the EGM, Scottish Green MSP Ross Greer insisted that the list of subjects could be changed if further agreements or disagreements emerge.
Ahead of the vote, the co-leaders insisted the agreement will be good for Scotland, the country's efforts to tackle the climate crisis and contains "transformational" policies such as implementing rent controls.
Mr Harvie said on Friday it feels "incredibly exciting" to be on the brink of government.
He added: "Our members will decide whether we're going to take this historic step and put Greens into government for the first time, not just in Scotland, but in any part of the UK."
The draft powersharing agreement was formally announced by First Minister and SNP leader Nicola Sturgeon along with the two Scottish Green co-leaders at her official residence, Bute House in Edinburgh, on August 20.
Announcing the deal, Ms Sturgeon stressed it is not a coalition but "about doing politics and governance better".
Negotiated over the summer after the SNP fell one seat short of an overall majority in May's election, the deal involves a shared policy platform agreed by both sides which would be pursued by the Scottish Government.
This includes an agreement to pursue another vote on Scottish independence before the end of 2023, if the threat of coronavirus has subsided.
It covers the majority of domestic policy, with 10 areas excluded where opinions differ.
The Scottish Conservatives branded the deal as creating a "coalition of chaos" focused on independence, while Scottish Labour said the "coalition of cuts" is a "disaster for Scotland".